Enable optional soft reset in AHCI

It occurred that some Marvell integrated controllers
require additional time after soft reset to work properly.
Introduce new quirk (AHCI_Q_MRVL_SR_DEL), that enable
such operation.

Submitted by: Konrad Adamczyk <ka@semihalf.com>
Obtained from: Semihalf
Sponsored by: Stormshield
Reviewed by: mav
Differential revision: https://reviews.freebsd.org/D9221